Ask a Horticulturist: How do I get rid of Fungus Gnats in My Houseplants?

Q: I was recently inspired by some work you did for the office I work in, and decided to create my own succulent arrangement at home. Within a few weeks, my arrangement started attracting these little fruit fly type gnats.  What are they? How do I get rid of them without using a chemical spray? A: I'm so happy you were inspired to get your hands in the dirt! I get asked this all the time: I love houseplants, but how do I prevent the gnats that come with them? The short answer is, you can't. I'm sorry, but for as long as there are house plants there will be fungus gnats that come with them. And that's what they are, by the way. Not fruit flies, but fungus gnats. Fungus gnat larvae lives in planting medium just below the surface. As the larvae matures into a fungus gnat it pushes it's way up through the surface of the soil and begins flying around your home.

As I said, you cannot prevent the larvae from occurring in planting medium. You can however, prevent the fungus gnats from leaving the earth and flying around your home. The easiest, eco-friendliest way to do this is to sprinkle the surface of the soil your houseplants are planted in with diatomaceous earth. Diatomaceous earth is a soft powder that is made from crumbled rock. What makes diatomaceous earth so effective is the structure of the individual grains. Since they are microscopic crumbled rock, they are very sharp around the edges. As the larvae pushes through the surface of the soil, it shreds the little guys before they have a chance to leave the plant.

If even this method seems to harsh, you can simply choose to ignore it. It won't go away, but the gnats are not harmful to you, pets or plants. They are just obnoxious.

Do you have a plant question or horticulture issue you'd like to chat about? Contact me for free advice about your gardening needs. La Fleur Plantscapes + Fresh Flora is committed to providingTucsonwith the greenest plant care for home, office, and events.